Simultaneous ambulatory 24-hour blood pressure monitoring and intraocular pressure-related patterns estimated with a contact-lens sensor in treated glaucoma patients.

Abstract

Purpose : Cross-sectional studies using single-day, snapshot measurements have shown that, between-patients, blood pressure (BP) and intraocular pressure (IOP) measurements correlate positively.[1,2] Yet, the investigation of the variability of these clinical parameters within-patients with simultaneous, semi-continuous monitoring during 24 hours has not yet been conducted. Here we test the hypothesis that IOP and BP patterns are correlated within treated glaucoma patients undergoing 24-hour monitoring.

Methods : 36 eyes (36 patients) with treated, established glaucoma underwent 24-hour BP and IOP-related measurements on the same day. IOP-related (IOPr) patterns were recorded with a validated contact-lens sensor (CLS, Sensimed Triggerfish^®; Sensimed AG) that captures spontaneous circumferential changes at the corneoscleral area due to volume changes, which are correlated with IOP.[3] The CLS recorded consecutive readings every 5 minutes for up to 30 seconds, at intervals of 100 milliseconds. BP measurements (Spacelabs, Inc.) were taken every 30 minutes from 10:00 pm to 7:00 am and every 15 minutes for the rest of the day. We estimated the IOPr variability with the Average Real Variability (ARV) index: ARV=1/(N-1) ∑ | P_k+1-P_k |. Additionally, generalized estimating equations (GEE) were used to test the relationship between IOP and systolic (SBP) and diastolic (DBP) BP within-patients over 24 hours.

Results : Pearson’s correlation revealed a significant, moderate correlation between IOPr ARVs and DBP (r =0.34, P=0.03). Further, GEE models revealed a significant relation between IOPr vs. DBP and IOPr vs. SBP within-patients (β=-1.87; 95% CI=-2.98 to -0.75; P=0.0010 and β=-1.42; 95% CI=-2.39 to -0.45; P=0.0039, respectively). The Figure below depicts the 24-hour patterns of average SBP, DBP, and IOPr of the 36 patients.

Conclusions : In glaucoma patients undergoing simultaneous 24-hour IOPr and BP measurements, higher DBP was associated with higher IOPr variability. Also, IOPr had a significant inverse relationship with both SBP and DBP. That is, IOPr was highest when BP was lowest. Impaired auto-regulation of these relationships could lead to optic nerve ischemia and progressive vision loss from glaucoma.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.